The present invention relates to a method of recovering volatile metals or concentrates thereof from material containing metal oxides.
In U.S. Pat. No. 4,072,504, for example, there is disclosed a method for recovering metals from material containing metal oxides by blowing the material together with a reducing agent into a shaft filled with coke. At the same time thermal energy is supplied so that at least a part of the metal content is reduced to metal and the non-volatile metal or metals are reduced out. The reduced metal and the slag are collected at the bottom of the shaft where they can be removed.
However, at present there is a need for a method of recovering volatile metals such as zinc, lead, sodium and potassium from crude products or ores containing a substantial percentage of oxides of iron and other non-volatile metals. This is mainly due to the fact that a volatile metal, after being reduced and volatilized, is recondensed or reoxidized in known process apparatus, which results in clogging or other problems in operation. In practice, therefore, it has been found that metals reduced primarily from the volatile group in conventional shafts condense in the upper part of the shaft in the vicinity of the blast furnace top, thus causing considerable operational problems. Furthermore, with conventional shafts, slight oxidation of, for instance, zinc is obtained, resulting in an undesirable blue-fraction being formed. As in known in the art, this problem is extremely difficult to solve.